Telephone system.



L. C. BYGRAVE.

TEL EPHONE SYSTEM. APPLICATION r1121) FEB. 12. 1916.

Patented Nov. 14, 1916.

ED STATES PATENT orFIc LEONARD CHARLES BYGRAVE, OF LONDON, ENGLAND, ASSIGNOR TO THE RELAY AUTOMATIC, TELEPHONE COMPANY, LIMITED, OF LONDON, ENGLAND. v

TELEPHONE SYSTEM.

Specification of Letters Patent.

Patented Nov. 14, 1916.

Application filed February 12, 1916. Serial No. 77,968.

, London, England, have invented new and useful Improvements in Telephone Systems, of which the following is a specification.

The invention relates to central battery telephone systems in which the calling sig nal eifected by a subscriber taking off his telephone is disconnected by a cut-off relay as soon as connection has been established with a cord circuit or a junction line, and has for its object to prevent unintentional calls caused by the disconnection of a talking circuit while a subscriber still keeps his telephone removed. More particularly the invention has for its object to prevent such false calling signals by means associated with the subscribers lines. Systems are known in which this object is attained by keeping the cut-off relay energized directly or indirectly over the line circuit. In systems in which the disconnection of the talking circuit is under the control of the subscriber and the line circuit therefore includes controlling means associated with a cord circuit or a junction line, this arrangement necessitates an additional bridge con nection across the line branches.

According to the present invention the additional bridge is dispensed with bythe cut-off relay or any other relay effecting the disconnection of the calling signal, being connected to the line circuit upon the disconnection of the talking circuit, while during the conversation the cut-off relay is maintained energized from the cord or junction line.

The switching means for connecting the cut-off relay to the line may consist of an auxiliary relay, which upon being denergized at the end of the conversation, closes the line circuit through the cut-oil relay, or it may consist of an additional armature provided on the cut-off relay and which falls ofi more quickly than the other armature, thereby switching the cut-off relay over to the line circuit.

The invention is applicable to automatic and semi-automatic telephone systems, and also to manual systems in which there is automatic disconnection of the cord circuits, for example, as described in British specification No. 16906 of 1912.

The invention is illustrated by the accompanying drawing, Figure 1 of Which shows such parts of the circuit of a subscribers llne near his jack as are necessary for the comprehension of the invention. Fig. 2

shows a modification.

InFig. 1, A. isthe usual line or call relay and B is a slow-acting relay of the line C, wh1ch ends 1n a jack D. E is an auxiliary relay .adapted to be energized in series with relay B, Only four circuits are concerned and these are numbered 1, 2, 3, 4. Circuit 1 is completed when the subscriber lifts his receiver and thus relay A is energized over the loop: it consequently closes circuit 2 and the lamp L glows. Circuit 3 is connected by a plug and energizes relays B and E. Relay B breaks circuit 2 and the lamp ceases to glow and relay E cuts off all connections to line. Should the connection be severed before thecalling subscriber has replaced his receiver, circuit 3 will be opened and relay E will be denergized and complete circuit 4 before relay B has had time to deenergize, so that relay B remains energized over the calling line until the receiver is replaced, thereby preventing a false call being made. l/Vhen the line is a called instead of a calling line, circuit 3 is completed over the calling plug and the circuits from line and cut-ofl relays to loop are also opened. When the power of disconnecting the circuit is in the hands of the calling party and he replaces the receiver. to sever the connection, circuit 3, beyond the point T, will be opened, and B and E will deenergize, provided the called party has also replaced his receiver; should, however, he fail to do so, relay E will deenergize, and circuit 4 be completed before B has had time to deenergize, so that B remains energized over the called line until the receiver is replaced. The line relay A will therefore be kept from energizing to initiate another connection. The combination therefore under such conditions prevents false calls being sent in, and apparatus and lines being brought into use unnecessarily.

It is evident from the above description i lay, but it has an individual circuit 5 which is controlled by the auxiliary relay E. When the line is called, circuit 3 is completed over the final switch. Relay E is energized, and closes circuit 5, whereby the cutoff relay B is operated to open the circuit of the line relay A. When the power of disconnecting the circuit is in the hands of the calling party only, and he replaces the receiver to sever the connection, circuit .3, beyond the point T, will be opened, and

E and B will deenergize, provided the called party has also replaced his receiver; should, however, he fail to do so, relay E will deenergize and the circuit a will be completed before B has had time to denergize, so that B remains energized over the called line until the receiver is replaced. The line relay A will therefore be kept from energizing to initiate another connection. The combination therefore under such conditions prevents false calls being sent in, and apparatus and lines being used unnecessarily.

I do not limit myself to the particular forms and circuits used, as it will be readily understood that modifications may be made to bring about similar results or to adapt the invention to different systems.

What I claim is 1. In a telephone system, a subscribers line, a call relay associated therewith, a calling circuit, a cut-off relay controlling the Copies of this patent may be obtained for calling circuit and switching means associated with the subscribers line and adapted to connect said cut-off relay with the line circuitupon the disconnection of the talking circuit.

2. In a telephone system, a subscribers line, a call relay associated therewith, a calling circuit, a cut-off relay controlling the calling circuit and an auxiliary relay associated with the subscribers line and adapted to connect said cut-off relay with the line circuit upon the disconnection of the talking circuit.

3. In a telephone system, a suhscribers line, a call relay associatedtherewith, a callmg circuit, a slow-acting cut off relay controlling the calling circuit and an auxiliary relay associated with the subscribers line and adapted to connect said cut-ofi' relay with the hue circuit upon the disconnection I of the talking circuit.

LEONARD CHARLES BYGRAVE.

five cents each, by addressing the Commissioner of Patents.

Washington, I). 0. 

